123456k's chemistry questions

[123456k]

2A(aq) + B(aq) -> C(aq) + 2D(aq)
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                                                                                    -
An initial mixture where all concentrations are 2 mol L  is allowed to reach quilibrium. At equilibrium, the concentration of substance C was measured to be 1.5 mol L-. Calculate the value of the equilibrium constant.

The answer is 0.07 but i got 9 D:

someone please help me.

[KL_tutor]

Alright so initially everything with 2 M. Assuming volume stayed the same we can just use mol/L in our mol calculations. The concentration of substance C reduced by 0.5 M. That means the reaction was going backwards. For every mol of substance C used, 2 of substance D were used, 2 of substance A were produced and 1 of B was produced. Thus we can conclude that:

[C] = 1.5 M
[D] = 2.0 - (2 x 0.5) = 1.0 M
[A] = 2.0 + (2 x 0.5) = 3.0 M
[B = 2.0 + 0.5 = 2.5 M

K =



or approximately 0.07

Hope that helped

[123456k]

Thank you so much!

[123456k]

If a solution of 50 mL of 0.2 mol L- NaOH is mixed with 50 mL of 0.1 mol L- HNO3, find the pH of the resulting solution.

answer is 12.7

HELP PLEASE

[b^3]

to find ph we need to find [H₃O⁺] ions
so you need to find the amount (mol) of each of each of the substances and then find how much of one is left over at the end
so equation is
NaOH + HNO₃ -> NaNO₃ +H₂O
so n(NaOH)=0.050*0.2=0.01mol
n(HNO₃)=0.050*0.1=.005mol
so ratio is 1:1 so NaOH is in excess
so n-excess(NaOH)=0.01-0.005=0.005mol
so [OH^-]=[NaOH]=n/v=0.005/0.1=0.05M
so now you know that [H₃O⁺]*[OH^-]=10^-14 M²
so [H₃O⁺]=10^-14/0.05=2.0*10^-13M
so ph=-log([H₃O⁺])=-log(2.0*10^-13)=12.7

[Graphite]

beaten

[123456k]

Some more questions:

1. Why the following cooking hints save energy.
Do not overfill electric kettles

2. Explain the difference between nuclear binding energy and the enrgy liberated during nuclear fusion.

3. when hydrogen nuclei undergo fusion, large quantities of energy are released.
explain why this reaction may proceed only at extremely high temperatures.

4. write chemical equations to show how the hydrogen isotope tritium, 3 H could be produced by fusion reactions  
                                                                                                                1

5. energy derived from wind and wave power is sometimes described as another form of solar energy. justify this statement.

                                                                                                                                      
6. Determine the temperature change in a calorimeter when 5.00g of CaCl2.6H2O dissolves in 200ml of water according to the equation
                       H2O
CaCl2.6H2O(s)----->Ca^2+(aq) + 2Cl^-(aq) Delta(triangle thingy) H= +18.0 kJmol^-

The calibration factor for the calorimeter under these conditions was found to be 825 J C^-1

answer: 0.498 C
                                                                                    

[tony3272]

Some more questions:

1. Why the following cooking hints save energy.
Do not overfill electric kettles

Requires more energy to heat up the water if there is a larger volume.

[HenryP]

6. n(CaCl2.6H2O) =
According to the equation, 18kJ of energy is released per mole so the amount of energy released is about 0.411 kJ = 411J
The calibration factor is given to be 825 J C^-1 so the temperature increase can be found by 411/825 which gives us 0.498C